Increase in the use of a sophisticated car stereo in recent years has caused an increase in theft of these stereos. In order to prevent the theft of the stereo, there has been many proposals. In accordance with one of the proposals, a removable panel having a plurality of push buttons for control of the stereo is attached to the body of the stereo.
FIG. 15 shows the above described prior art. The car stereo comprises a car stereo body 10 and a removable panel 20 attached to the body 10. The body 10 has recessed panel 11 mounted at the front thereof. The panel 11 has a cassette opening 14. A detector switch 15 is provided on an upper left hand side of the panel 20 to mechanically detect the attachment of the panel 20 on the body 10. A connector 12 which is connected to a connector 21 (FIG. 16) provided at the back of the panel 20 when the panel is attached, are formed on the panel 11. The panel 20 has a cassette opening 24 which coincides with the cassette opening 14 of the body 10 and various operation keys 22. A display 23 is disposed at a central portion of the panel 20 so as to indicate information such as current time and the received frequency of the stereo.
Referring to FIG. 16 the connector 12 of the body 10 has a 5 V supply terminal 12a, data input/output terminal 12b, 8 V supply terminal 12c, and ground terminal 12d. The terminals 12a and 12c are connected to a 5 V supply circuit 17 and an 8 V supply circuit 18, respectively. The data input/output terminal 12b is connected to a microcomputer 19. The microcomputer 19 is connected to the detector switch 15 so as to be operated in accordance with the operating state of the switch 15.
The connector 21 of the panel 20 has terminals which correspond to the terminals 12a to 12d of the connector 12. Namely, there is provided a 5 V input terminal 21a, data input/output terminal 21b, 8 V input terminal 21c, and ground terminal 21d. The terminal 21a is connected to a microcomputer 25 so as to supply a 5 V voltage thereto. The microcomputer 25 receives data from the microcomputer 19 through the data input/output terminals 12b and 21b dependent on the operation of the operation keys 22 on the panel 20, such as the time and the frequency of the radio. The microcomputer 25 applies a control signal to a display driver 26 to indicate the received data on the display 23. The 8 V input terminal 21c is connected to a lamp 27 for lighting the display 23.
When the panel 20 is attached to the body 10, the terminals 21a to 21d of the connector 21 are connected to the respective terminals 12a to 12d of the connector 12. Accordingly, the 5 V supply circuit 17 and the 8 V supply circuit 18 are connected to the microcomputer 25 and the lamp 27, respectively, thereby operating them. The microcomputer 25 is applied with various data from the microcomputer 19 through the terminals 12b and 21b, so that, the microcomputer 25 operates to drive the display 23, thereby indicating information on the display 23.
On the contrary, when the panel 20 is detached, the detector switch 15 is opened. The microcomputer 19 stops feeding the data to the microcomputer 25. Thus the display 23 of the panel 20 does not show information.
When the panel 20 is removed from the stereo body 10, the stereo body 10 does not have the appearance of a car stereo. Hence, if the driver takes the panel 20 with him when leaving the vehicle, the theft of the car stereo is prevented.
However, since the panel detached from the stereo body 10 is utterly useless and hence will only be a hindrance, the driver is often reluctant to carry the panel around.